Most modern vehicles today have some form of air conditioning system installed for the comfort of the vehicle's operator and passengers. The air conditioning typically includes an air conditioning compressor powered by the vehicle's engine. The compressor is usually connected to the engine by a belt which connects a driving pulley on the engine to a pulley on the compressor. Further, the pulley on the compressor is typically connected to the compressor using some form of clutch mechanism. This clutch mechanism allows the compressor to be engaged or disengaged from the engine whenever the air conditioning is turned on or off. This prevents unnecessarily loading down the engine, saves fuel and reduces wear and tear on the various components involved.
It is common for such vehicle air conditioning compressors to fail when a bearing seizes, lubrication fails or other components break causing the compressor to substantially slow down or seize completely. When this happens, the load on the engine or the belt and clutch mechanism increases substantially. This could potentially result in serious damage to the engine, belt or clutch or further damage to the compressor. In engines utilizing a single belt to connect the compressor, the cooling fan and other components, the breakage of the belt can cause overheating of the engine which can result in serious damage.
U.S. Pat. No. 4,462,491 discloses a monitoring system to detect failure of the air conditioning compressor and disengage the compressor in the event of such failure. The disclosed system uses one or more sensors to detect the rotation of the pulleys on the engine and on the compressor. When the rotations of the engine pulley and the compressor pulley diverge by a pre-set amount, or when the rotation of the compressor pulley falls below a pre-set threshold, the monitoring system determines that a failure has occurred and disengages the compressor from the engine. This system keeps the compressor disengaged as long as the particular failure conditions are present. This system is not capable of distinguishing between different types of failures and therefore responds to any failure in the same way.
Accordingly there is a need for an improved monitoring apparatus which monitors a secondary load coupled to a primary mover and disengages the secondary load upon detection of a failure. Further, there is a need for a monitoring apparatus which provides a staged response to different failure situations and which has the ability to correct minor failures and mitigate damage caused by major failures. Still further, there is a need for monitoring apparatus which retains information regarding prior failures and prevents operation of the primary mover or secondary load before the prior failure has been repaired.